In one form of known power transmission belt adapted for transmitting high loads, an endless steel band is provided with a plurality of V-shaped metal blocks. Examples of such constructions are shown in U.S. Pat. Nos. 3,949,621, 4,303,403, and 4,342,561. As shown therein, each block is mounted to the steel band and includes a projection and recess on one side of the head surface. The blocks are longitudinally spaced and are arranged in face-to-face abutting relationship to the steel band.
Such power transmission belts, while providing for high load transmission, have not proven completely satisfactory in the art because of the substantial weight thereof. Further, such belts generate high levels of noise requiring sound deadening means, such as oil baths and the like.
In U.S. Pat No. 4,365,965, a V-block belt is shown having a flat belt portion formed of a polymeric resin and having V-blocks mounted thereto formed of polymeric resin. As disclosed therein, the belt construction is extremely complicated and expensive.
In U.S. Pat No. 4,305,714, a heavy duty power transmission belt is shown to be formed of a lamination of rubber impregnated fabric on a lower surface portion of a cushion rubber layer so as to provide cog projections on the inner surface of the belt for engagement with a drive pulley. While this belt construction provides improved flexibility, it has a decreased ability to transmit high loads as a result of the intrusion into the pulley of the cushion rubber material which is conventionally of relatively high resiliency. Another attempt to resolve this vexatious problem has been the employment of metal rods or pipes or wooden elements in the cogged portion of the belt. Such materials are disadvantageous in that wood is relatively weak and, when heated, the synthetic resin strength characteristics decrease. Such heating normally occurs from the engagement of the belt with the pulley in the drive operation. Thus, such belts have been found to present serious problems in the reduction in strength and wear resistance.
In one form of the belt, the cogged portion is formed of aluminum in an effort to reduce the weight. Aluminum, however, has been found to present disadvantages in the low wear resistance thereof.
More recently, still another form of power transmission belt adapted for high load transmission has been developed, as illustrated in FIG. 3 of the drawing hereof. As shown therein, the prior art belt includes a tensile cord midportion, an outer reinforcing plate portion, and an inner trapezoidal block portion. Bolts are extended through the belt to secure the plate and block portions to the tensile cord portion.
In Japanese Utility Model Application No. 48727/1983, a cogged block structure for use in such a belt is disclosed as being formed of a cloth wrapped in a spiral and impregnated with either rubber of thermosetting resin. By wrapping the cloth or fabric spirally, a more rigid block is provided compared with a block formed of a plurality of flat laminated fabric layers. Such a block, however, has been found to have the vexatious problem of high noise generation. If the rigidity of the block is decreased to suppress the noise, its transmitting force has been found to be adversely decreased. The prior art belts of this configuration have had the disadvantages of relatively high weight and cost and inconvenience in handling.